A dopamine-responsive growth factor has recently been identified. Findings that the activity of this growth factor is increased in the CSF of patients with Parkinson's disease and in brain extracts of neuroleptic-treated rats suggest that damage or perturbation of the dopaminergic system may be related to elaboration of specific growth factors. Since a possible abnormality of the dopaminergic system has been implicated in schizophrenia, and since neuroleptic (dopamine blocking) drugs are nearly always used in its medical treatment, we elected to examine the activity of this growth factor in the CSF of medicated and unmedicated schizophrenic subjects and normal controls. Our data shows no difference in dopamine-responsive growth factor activity in the schizophrenic group compared to controls. Since we could not replicate the observed neuroleptic effect in brain extracts of rats, it is concluded that the assay, in its current form, is not sensitive enough to detect subtle elaborations of this growth factor.